Intelligent Optical Systems proposes to develop InVITME, an implantable sensor system for in vivo clinical continuous monitoring of the chemistry within the tumor microenvironment (TME) during drug trials, which will increase the pace of TME-targeted drug discovery and may improve early stage diagnosis, prognosis assessment, prediction of effective therapy, and therapy modulation during treatment. The probe will make use of fiber optic microsensors developed by IOS and already demonstrated in vivo. We will combine our fiber optic sensors with a revolutionary new way of processing analog signals on digital components. These designs, pioneered by Circuit Seed, LLC, all have 100% digital workflow components, overcoming many of the restrictions of traditional analog circuits, including size, precision, and power requirements. Our implantable probe-based design has many important advantages: the implantation procedure needs to be performed only once, and will collect orders of magnitude more data than periodic assessment by imaging, and neither expensive instrument time nor the presence of a physician or technician is required to gather data. Large studies could be conducted, with data being logged and analyzed remotely for many patients, so that large datasets can be collected inexpensively.